Replicating using volume multiplexing with consistency group file

ABSTRACT

In one aspect, a method includes replicating a first volume to a consistency group (CG) file on a backup device. The method also includes replicating a second volume to the CG file concurrently with the replicating of the first volume, the first and second volumes being in a consistency group.

BACKGROUND

Computer data is vital to today's organizations and a significant partof protection against disasters is focused on data protection. Assolid-state memory has advanced to the point where cost of memory hasbecome a relatively insignificant factor, organizations can afford tooperate with systems that store and process terabytes of data.

Conventional data protection systems include tape backup drives, forstoring organizational production site data on a periodic basis. Anotherconventional data protection system uses data replication, by generatinga copy of production site data of an organization on a secondary backupstorage system, and updating the backup with changes. The backup storagesystem may be situated in the same physical location as the productionstorage system, or in a physically remote location. Data replicationsystems generally operate either at the application level, at the filesystem level, or at the data block level.

SUMMARY

In one aspect, a method includes replicating a first volume to aconsistency group (CG) file on a backup device. The method also includesreplicating a second volume to the CG file concurrently with thereplicating of the first volume, the first and second volumes being in aconsistency group.

In another aspect, an apparatus includes electronic hardware circuitryconfigured to replicate a first volume to a consistency group (CG) fileon a backup device and replicate a second volume to the CG fileconcurrently with the replicating of the first volume, the first andsecond volumes being in a consistency group.

In a further aspect, an article includes a non-transitorycomputer-readable medium that stores computer-executable instructions.The instructions cause a machine to replicate a first volume to aconsistency group (CG) file on a backup device and replicate a secondvolume to the CG file concurrently with the replicating of the firstvolume, the first and second volumes being in a consistency group.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example of a data protection system.

FIG. 2 is an illustration of an example of a journal history of writetransactions for a storage system.

FIG. 3 is a block diagram of an example of a system to initialize abackup snapshot.

FIG. 4 is a flowchart of an example of a process to initialize a backupsnapshot.

FIG. 5 is a block diagram of an example of a system to initialize abackup snapshot.

FIG. 6 is a block diagram of an example of a system to synthesize newbackup snapshots.

FIG. 7 is a flowchart of an example of a process to synthesize newbackup snapshots.

FIG. 7A is a flowchart of an example, of a process to generate asynthesis plan.

FIG. 8 is a block diagram of an example of a system to recoverpoint-in-time data.

FIG. 9 is a flowchart of an example, of a process to recoverpoint-in-time data.

FIG. 10 is a simplified diagram depicting data protection windowsproviding backup granularity.

FIG. 11 is a block diagram of another example of a data protectionsystem using volume multiplexing.

FIG. 12 is a flowchart of an example of a process to perform snapshotreplication to a backup device.

FIG. 13A is a block diagram of an example of a CG file.

FIG. 13B is a block diagram of an example of a copy of a CG file at apoint-in-time.

FIG. 13C is a block diagram of an example of a recovering a volume usingthe process of FIG. 15.

FIG. 13D is a block diagram of an example of a CG file after a newvolume has been added using a process of FIG. 16.

FIG. 13E is a block diagram of an example of a CG file after a volumehas been deleted using a process of FIG. 17.

FIG. 13F is a block diagram of an example of a CG file after volume hasbeen resized using a process of FIG. 18.

FIG. 14 is a flowchart of an example of a process to protect data usingthe data protection system of FIG. 11.

FIG. 15 is a flowchart of an example of a process to restore protecteddata from the data protection system of FIG. 11.

FIG. 16 is a flowchart of an example of a process to add a volume to aconsistency group (CG) file in the data protection system of FIG. 11.

FIG. 17 is a flowchart of an example of a process to remove a volumefrom the CG file in the data protection system of FIG. 11.

FIG. 18 is a flowchart of an example of a process to resize a volume andresize the CG file in the data protection system of FIG. 11.

FIG. 19 is a simplified block diagram of an example of a computer onwhich any of the processes of FIGS. 4, 7, 7A, 9, 12 and 14 to 18 may beimplemented.

DETAILED DESCRIPTION

Described herein are techniques to perform continuous data protectionusing volume multiplexing.

The following definitions may be useful in understanding thespecification and claims.

BACKUP SITE—a facility where replicated production site data is stored;the backup site may be located in a remote site or at the same locationas the production site; a backup site may be a virtual or physical site.

BOOKMARK—a bookmark is metadata information stored in a replicationjournal which indicates a point in time.

CDP—Continuous Data Protection, a full replica of a volume or a set ofvolumes along with a journal which allows any point in time access, theCDP copy is at the same site, and maybe the same storage array of theproduction site.

DATA PROTECTION APPLIANCE (DPA)—a computer or a cluster of computers, ora set of processes that serve as a data protection appliance,responsible for data protection services including inter alia datareplication of a storage system, and journaling of I/O requests issuedby a host computer to the storage system. The DPA may be a physicaldevice, a virtual device running, or may be a combination of a virtualand physical device.

DEDUPLICATED STORAGE SYSTEM—any storage system capable of storingdeduplicated or space reduced data, and in some examples, is an EMC®DataDomain® system. Deduplicated data may also be any data that isprocessed to remove redundant data.

HOST—at least one computer or networks of computers that runs at leastone data processing application that issues I/O requests to one or morestorage systems; a host is an initiator with a SAN.

HOST DEVICE—an internal interface in a host, to a logical storage unit.

IMAGE—a copy of a logical storage unit at a specific point in time.

INITIATOR—a node in a SAN that issues I/O requests.

I/O REQUEST—an input/output request (sometimes referred to as an I/O orIO), which may be a read I/O request (sometimes referred to as a readrequest or a read) or a write I/O request (sometimes referred to as awrite request or a write).

JOURNAL—a record of write transactions issued to a storage system; usedto maintain a duplicate storage system, and to roll back the duplicatestorage system to a previous point in time.

LOGICAL UNIT—a logical entity provided by a storage system for accessingdata from the storage system. The logical disk may be a physical logicalunit or a virtual logical unit.

LUN—a logical unit number for identifying a logical unit.

PHYSICAL LOGICAL UNIT—a physical entity, such as a disk or an array ofdisks, for storing data in storage locations that can be accessed byaddress.

PRODUCTION SITE—a facility where one or more host computers run dataprocessing applications that write data to a storage system and readdata from the storage system.

REMOTE ACKNOWLEDGEMENTS—an acknowledgement from remote DPA to the localDPA that data arrived at the remote DPA (either to the appliance or thejournal).

SNAPSHOT—a snapshot is an image or differential representations of animage, i.e., the snapshot may have pointers to the original volume, andmay point to log volumes for changed locations. Snapshots may becombined into a snapshot array, which may represent different imagesover a time period.

SPLITTER/PROTECTION AGENT—is an agent running either on a productionhost a switch or a storage array which can intercept Ms and split themto a DPA and to the storage array, fail Ms, redirect I/Os or do anyother manipulation to the I/O; the splitter or protection agent may beused in both physical and virtual systems. The splitter may be in theI/O stack of a system and may be located in the hypervisor for virtualmachines. In some examples, a splitter may be referred to as an OpenReplicator Splitter (ORS).

SPLITTER ACKNOWLEDGEMENT—an acknowledgement from a DPA to the protectionagent (splitter) that data has been received at the DPA; this may beachieved by an SCSI status command.

SAN—a storage area network of nodes that send and receive an I/O andother requests, each node in the network being an initiator or a target,or both an initiator and a target.

SOURCE SIDE—a transmitter of data within a data replication workflow,during normal operation a production site is the source side; and duringdata recovery a backup site is the source side, sometimes called aprimary side. Source side may be a virtual or physical site.

STORAGE SYSTEM—a SAN entity that provides multiple logical units foraccess by multiple SAN initiators.

STREAMING—transmitting data in real time, from a source to adestination, as the data is read or generated.

SYNTHESIZE—generating a new file, for example, using pointers fromexisting files, without actually copying the referenced data. In oneparticular example, a new file representing a volume at a points-in-timemay be generated using pointers to a file representing a previouspoint-in-time, as well pointers to journal representing changes to thevolume.

TARGET—a node in a SAN that replies to I/O requests.

TARGET SIDE—a receiver of data within a data replication workflow;during normal operation a back site is the target side, and during datarecovery a production site is the target side, sometimes called asecondary side. The target side may be a virtual or physical site.

THIN PROVISIONING—thin provisioning involves the allocation of physicalstorage when it is needed rather than allocating the entire physicalstorage in the beginning Thus, use of thin provisioning is known toimprove storage utilization.

THIN LOGICAL UNIT—a thin logical unit is a logical unit that uses thinprovisioning.

VIRTUAL LOGICAL UNIT—a virtual storage entity which is treated as alogical unit by virtual machines.

WAN—a wide area network that connects local networks and enables them tocommunicate with one another, such as the Internet.

A description of journaling and some techniques associated withjournaling may be described in the patent titled “METHODS AND APPARATUSFOR OPTIMAL JOURNALING FOR CONTINUOUS DATA REPLICATION” and with U.S.Pat. No. 7,516,287, which is hereby incorporated by reference.

Referring to FIG. 1, a data protection system 100 includes two sites;Site I, which is a production site, and Site II, which is a backup siteor replica site. Under normal operation the production site is thesource side of system 100, and the backup site is the target side of thesystem. The backup site is responsible for replicating production sitedata. Additionally, the backup site enables roll back of Site I data toan earlier pointing time, which may be used in the event of datacorruption of a disaster, or alternatively in order to view or to accessdata from an earlier point in time.

FIG. 1 is an overview of a system for data replication of eitherphysical or virtual logical units. Thus, one of ordinary skill in theart would appreciate that in a virtual environment a hypervisor, in oneexample, would consume logical units and generate a distributed filesystem on them such as VMFS generates files in the file system andexpose the files as logical units to the virtual machines (each VMDK isseen as a SCSI device by virtual hosts). In another example, thehypervisor consumes a network based file system and exposes files in theNFS as SCSI devices to virtual hosts.

During normal operations, the direction of replicate data flow goes fromsource side to target side. It is possible, however, for a user toreverse the direction of replicate data flow, in which case Site Istarts to behave as a target backup site, and Site II starts to behaveas a source production site. Such change of replication direction isreferred to as a “failover”. A failover may be performed in the event ofa disaster at the production site, or for other reasons. In some dataarchitectures, Site I or Site II behaves as a production site for aportion of stored data, and behaves simultaneously as a backup site foranother portion of stored data. In some data architectures, a portion ofstored data is replicated to a backup site, and another portion is not.

The production site and the backup site may be remote from one another,or they may both be situated at a common site, local to one another.Local data protection has the advantage of minimizing data lag betweentarget and source, and remote data protection has the advantage is beingrobust in the event that a disaster occurs at the source side.

The source and target sides communicate via a wide area network (WAN)128, although other types of networks may be used.

Each side of system 100 includes three major components coupled via astorage area network (SAN); namely, (i) a storage system, (ii) a hostcomputer, and (iii) a data protection appliance (DPA). Specifically withreference to FIG. 1, the source side SAN includes a source host computer104, a source storage system 108, and a source DPA 112. Similarly, thetarget side SAN includes a target host computer 116, a target storagesystem 120, and a target DPA 124. As well, the protection agent(sometimes referred to as a splitter) may run on the host, or on thestorage, or in the network or at a hypervisor level, and that DPAs areoptional and DPA code may run on the storage array too, or the DPA 124may run as a virtual machine.

Generally, a SAN includes one or more devices, referred to as “nodes”. Anode in a SAN may be an “initiator” or a “target”, or both. An initiatornode is a device that is able to initiate requests to one or more otherdevices; and a target node is a device that is able to reply torequests, such as SCSI commands, sent by an initiator node. A SAN mayalso include network switches, such as fiber channel switches. Thecommunication links between each host computer and its correspondingstorage system may be any appropriate medium suitable for data transfer,such as fiber communication channel links.

The host communicates with its corresponding storage system using smallcomputer system interface (SCSI) commands.

System 100 includes source storage system 108 and target storage system120. Each storage system includes physical storage units for storingdata, such as disks or arrays of disks. Typically, storage systems 108and 120 are target nodes. In order to enable initiators to send requeststo storage system 108, storage system 108 exposes one or more logicalunits (LU) to which commands are issued. Thus, storage systems 108 and120 are SAN entities that provide multiple logical units for access bymultiple SAN initiators.

Logical units are a logical entity provided by a storage system, foraccessing data stored in the storage system. The logical unit may be aphysical logical unit or a virtual logical unit. A logical unit isidentified by a unique logical unit number (LUN). Storage system 108exposes a logical unit 136, designated as LU A, and storage system 120exposes a logical unit 156, designated as LU B.

LU B is used for replicating LU A. As such, LU B is generated as a copyof LU A. In one example, LU B is configured so that its size isidentical to the size of LU A. Thus, for LU A, storage system 120 servesas a backup for source side storage system 108. Alternatively, asmentioned hereinabove, some logical units of storage system 120 may beused to back up logical units of storage system 108, and other logicalunits of storage system 120 may be used for other purposes. Moreover,there is symmetric replication whereby some logical units of storagesystem 108 are used for replicating logical units of storage system 120,and other logical units of storage system 120 are used for replicatingother logical units of storage system 108.

System 100 includes a source side host computer 104 and a target sidehost computer 116. A host computer may be one computer, or a pluralityof computers, or a network of distributed computers, each computer mayinclude inter alia a conventional CPU, volatile and non-volatile memory,a data bus, an I/O interface, a display interface and a networkinterface. Generally a host computer runs at least one data processingapplication, such as a database application and an e-mail server.

Generally, an operating system of a host computer generates a hostdevice for each logical unit exposed by a storage system in the hostcomputer SAN. A host device is a logical entity in a host computer,through which a host computer may access a logical unit. Host device 104identifies LU A and generates a corresponding host device 140,designated as Device A, through which it can access LU A. Similarly,host computer 116 identifies LU B and generates a corresponding device160, designated as Device B.

In the course of continuous operation, host computer 104 is a SANinitiator that issues I/O requests (write/read operations) through hostdevice 140 to LU A using, for example, SCSI commands. Such requests aregenerally transmitted to LU A with an address that includes a specificdevice identifier, an offset within the device, and a data size. Offsetsare generally aligned to 512 byte blocks. The average size of a writeoperation issued by host computer 104 may be, for example, 10 kilobytes(KB); i.e., 20 blocks. For an I/O rate of 50 megabytes (MB) per second,this corresponds to approximately 5,000 write transactions per second.

System 100 includes two data protection appliances, a source side DPA112 and a target side DPA 124. A DPA performs various data protectionservices, such as data replication of a storage system, and journalingof I/O requests issued by a host computer to source side storage systemdata. As explained in detail herein, when acting as a target side DPA, aDPA may also enable roll back of data to an earlier point in time, andprocessing of rolled back data at the target site. Each DPA 112 and 124is a computer that includes inter alia one or more conventional CPUs andinternal memory.

For additional safety precaution, each DPA is a cluster of suchcomputers. Use of a cluster ensures that if a DPA computer is down, thenthe DPA functionality switches over to another computer. The DPAcomputers within a DPA cluster communicate with one another using atleast one communication link suitable for data transfer via fiberchannel or IP based protocols, or such other transfer protocol. Onecomputer from the DPA cluster serves as the DPA leader. The DPA clusterleader coordinates between the computers in the cluster, and may alsoperform other tasks that require coordination between the computers,such as load balancing.

In the architecture illustrated in FIG. 1, DPA 112 and DPA 124 arestandalone devices integrated within a SAN. Alternatively, each of DPA112 and DPA 124 may be integrated into storage system 108 and storagesystem 120, respectively, or integrated into host computer 104 and hostcomputer 116, respectively. Both DPAs communicate with their respectivehost computers through communication lines such as fiber channels using,for example, SCSI commands or any other protocol.

DPAs 112 and 124 are configured to act as initiators in the SAN; i.e.,they can issue I/O requests using, for example, SCSI commands, to accesslogical units on their respective storage systems. DPA 112 and DPA 124are also configured with the necessary functionality to act as targets;i.e., to reply to I/O requests, such as SCSI commands, issued by otherinitiators in the SAN, including inter alia their respective hostcomputers 104 and 116. Being target nodes, DPA 112 and DPA 124 maydynamically expose or remove one or more logical units.

As described hereinabove, Site I and Site II may each behavesimultaneously as a production site and a backup site for differentlogical units. As such, DPA 112 and DPA 124 may each behave as a sourceDPA for some logical units, and as a target DPA for other logical units,at the same time.

Host computer 104 and host computer 116 include protection agents 144and 164, respectively. Protection agents 144 and 164 intercept SCSIcommands issued by their respective host computers, via host devices tological units that are accessible to the host computers. A dataprotection agent may act on an intercepted SCSI commands issued to alogical unit, in one of the following ways: send the SCSI commands toits intended logical unit; redirect the SCSI command to another logicalunit; split the SCSI command by sending it first to the respective DPA;after the DPA returns an acknowledgement, send the SCSI command to itsintended logical unit; fail a SCSI command by returning an error returncode; and delay a SCSI command by not returning an acknowledgement tothe respective host computer.

A protection agent may handle different SCSI commands, differently,according to the type of the command. For example, a SCSI commandinquiring about the size of a certain logical unit may be sent directlyto that logical unit, while a SCSI write command may be split and sentfirst to a DPA associated with the agent. A protection agent may alsochange its behavior for handling SCSI commands, for example as a resultof an instruction received from the DPA.

Specifically, the behavior of a protection agent for a certain hostdevice generally corresponds to the behavior of its associated DPA withrespect to the logical unit of the host device. When a DPA behaves as asource site DPA for a certain logical unit, then during normal course ofoperation, the associated protection agent splits I/O requests issued bya host computer to the host device corresponding to that logical unit.Similarly, when a DPA behaves as a target device for a certain logicalunit, then during normal course of operation, the associated protectionagent fails I/O requests issued by host computer to the host devicecorresponding to that logical unit.

Communication between protection agents and their respective DPAs mayuse any protocol suitable for data transfer within a SAN, such as fiberchannel, or SCSI over fiber channel. The communication may be direct, orvia a logical unit exposed by the DPA. Protection agents communicatewith their respective DPAs by sending SCSI commands over fiber channel.

Protection agents 144 and 164 are drivers located in their respectivehost computers 104 and 116. Alternatively, a protection agent may alsobe located in a fiber channel switch, or in any other device situated ina data path between a host computer and a storage system or on thestorage system itself. In a virtualized environment, the protectionagent may run at the hypervisor layer or in a virtual machine providinga virtualization layer.

What follows is a detailed description of system behavior under normalproduction mode, and under recovery mode.

In production mode DPA 112 acts as a source site DPA for LU A. Thus,protection agent 144 is configured to act as a source side protectionagent; i.e., as a splitter for host device A. Specifically, protectionagent 144 replicates SCSI I/O write requests. A replicated SCSI I/Owrite request is sent to DPA 112. After receiving an acknowledgementfrom DPA 124, protection agent 144 then sends the SCSI I/O write requestto LU A. After receiving a second acknowledgement from storage system108 host computer 104 acknowledges that an I/O command complete.

When DPA 112 receives a replicated SCSI write request from dataprotection agent 144, DPA 112 transmits certain I/O informationcharacterizing the write request, packaged as a “write transaction”,over WAN 128 to DPA 124 on the target side, for journaling and forincorporation within target storage system 120.

DPA 112 may send its write transactions to DPA 124 using a variety ofmodes of transmission, including inter alia (i) a synchronous mode, (ii)an asynchronous mode, and (iii) a snapshot mode. In synchronous mode,DPA 112 sends each write transaction to DPA 124, receives back anacknowledgement from DPA 124, and in turns sends an acknowledgement backto protection agent 144. Protection agent 144 waits until receipt ofsuch acknowledgement before sending the SCSI write request to LU A.

In asynchronous mode, DPA 112 sends an acknowledgement to protectionagent 144 upon receipt of each I/O request, before receiving anacknowledgement back from DPA 124.

In snapshot mode, DPA 112 receives several I/O requests and combinesthem into an aggregate “snapshot” of all write activity performed in themultiple I/O requests, and sends the snapshot to DPA 124, for journalingand for incorporation in target storage system 120. In snapshot mode DPA112 also sends an acknowledgement to protection agent 144 upon receiptof each I/O request, before receiving an acknowledgement back from DPA124.

For the sake of clarity, the ensuing discussion assumes that informationis transmitted at write-by-write granularity.

While in production mode, DPA 124 receives replicated data of LU A fromDPA 112, and performs journaling and writing to storage system 120. Whenapplying write operations to storage system 120, DPA 124 acts as aninitiator, and sends SCSI commands to LU B.

During a recovery mode, DPA 124 undoes the write transactions in thejournal, so as to restore storage system 120 to the state it was at, atan earlier time.

As described hereinabove, LU B is used as a backup of LU A. As such,during normal production mode, while data written to LU A by hostcomputer 104 is replicated from LU A to LU B, host computer 116 shouldnot be sending I/O requests to LU B. To prevent such I/O requests frombeing sent, protection agent 164 acts as a target site protection agentfor host Device B and fails I/O requests sent from host computer 116 toLU B through host Device B.

Target storage system 120 exposes a logical unit 176, referred to as a“journal LU”, for maintaining a history of write transactions made to LUB, referred to as a “journal”. Alternatively, journal LU 176 may bestriped over several logical units, or may reside within all of or aportion of another logical unit. DPA 124 includes a journal processor180 for managing the journal.

Journal processor 180 functions generally to manage the journal entriesof LU B. Specifically, journal processor 180 enters write transactionsreceived by DPA 124 from DPA 112 into the journal, by writing them intothe journal LU, reads the undo information for the transaction from LUB. updates the journal entries in the journal LU with undo information,applies the journal transactions to LU B, and removes already-appliedtransactions from the journal.

Referring to FIG. 2, which is an illustration of a write transaction 200for a journal. The journal may be used to provide an adaptor for accessto storage 120 at the state it was in at any specified point in time.Since the journal includes the “undo” information necessary to roll backstorage system 120, data that was stored in specific memory locations atthe specified point in time may be obtained by undoing writetransactions that occurred subsequent to such point in time.

Write transaction 200 generally includes the following fields: one ormore identifiers; a time stamp, which is the date & time at which thetransaction was received by source side DPA 112; a write size, which isthe size of the data block; a location in journal LU 176 where the datais entered; a location in LU B where the data is to be written; and thedata itself.

Write transaction 200 is transmitted from source side DPA 112 to targetside DPA 124. As shown in FIG. 2, DPA 124 records the write transaction200 in the journal that includes four streams. A first stream, referredto as a DO stream, includes new data for writing in LU B. A secondstream, referred to as an DO METADATA stream, includes metadata for thewrite transaction, such as an identifier, a date & time, a write size, abeginning address in LU B for writing the new data in, and a pointer tothe offset in the DO stream where the corresponding data is located.Similarly, a third stream, referred to as an UNDO stream, includes olddata that was overwritten in LU B; and a fourth stream, referred to asan UNDO METADATA, include an identifier, a date & time, a write size, abeginning address in LU B where data was to be overwritten, and apointer to the offset in the UNDO stream where the corresponding olddata is located.

In practice each of the four streams holds a plurality of writetransaction data. As write transactions are received dynamically bytarget DPA 124, they are recorded at the end of the DO stream and theend of the DO METADATA stream, prior to committing the transaction.During transaction application, when the various write transactions areapplied to LU B, prior to writing the new DO data into addresses withinthe storage system, the older data currently located in such addressesis recorded into the UNDO stream. In some examples, the metadata stream(e.g., UNDO METADATA stream or the DO METADATA stream) and the datastream (e.g., UNDO stream or DO stream) may be kept in a single streameach (i.e., one UNDO data and UNDO METADATA stream and one DO data andDO METADATA stream) by interleaving the metadata into the data stream.

FIGS. 3 to 5 depict systems and processes for initializing a backupsnapshot on deduplicated storage consistent. Before deduplicated storagecan provide continuous backup protection, it may be necessary togenerate an initial backup snapshot of the source storage system. Thisinitial backup snapshot may represent the earliest point-in-time backupthat may be restored. As changes are made to the source storage system,journal files and/or new backups may be updated and/or synthesized toprovide continuous protection. In some examples, the initial backupsnapshot may be generated by streaming I/Os from a storage system scanto a data protection appliance, or by taking an initial snapshot of thestorage system and transmitting the entire snapshot to deduplicatedstorage.

FIG. 3 depicts a system for generating an initial backup snapshot byscanning a source storage system and streaming I/Os to the deduplicatedstorage. Data protection application 300 may include journal processor302, and may be in communication with deduplicated storage 304. In oneexample, deduplicated storage 304 may be target side storage residing ata backup site. Data protection appliance 300 may be similar to dataprotection appliance 112 and/or 124, and may be responsible forstreaming I/Os to deduplicated storage 304.

In one example, a source storage system may be scanned and individualoffsets may be streamed to data protection appliance 300. The offsetsstreamed from the scanned system may be referred to as initializationI/Os, and may be streamed sequentially to data protection appliance 300.For example, the scanned system may include offsets 0, 1, 2, and 3,comprising data A, B, C, and D. The initial scan may start at thebeginning of the system, and transmit offset 0, followed by offset 1,and so forth.

As data protection appliance 300 receives the initialization I/Os,journal processor 302 may identify the offset data and metadata, and maystream the I/Os to metadata journal 306 and/or data journal 308 residingon deduplicated storage 304. Data journal 308 may include data storedwithin an offset, and metadata 306 may include metadata associated withthat offset. Metadata could include, for example, an offset identifier,size, write time, and device ID. These journals may then be used tosynthesize a backup snapshot on deduplicated storage 304, as describedherein.

In some examples, a scanned storage system may operate in a liveenvironment. As a result, applications may be writing to the storageconcurrently with the scan process. If an application writes to alocation that has already been streamed, the journal files andultimately the synthesized snapshot may be out of date. To address thisissue, application I/Os may be streamed concurrently with theinitialization I/Os if the application I/Os are to an offset that hasalready been scanned. For example, consider Table 1:

Time Offset t0 t1 t2 t3 0 A A′ 1 B B′ 2 C 3 D D′

Table 1 depicts four different offsets, denoted as 0, 1, 2, and 3, andfour times, t0, t1, t2, and t3. Letters A, B, C, and D may represent thedata stored at the offsets. Time t0 may represent the offsets as theyexist when the scan begins. These offsets may be streamed to dataprotection appliance 300 sequentially from 0 to 3. At time t1, however,the data at offset 1 is modified by an application from B to B′.Similarly, at t2 the data at offset 3 changes from D to D′, and at t3the data at offset 0 changes from A to A′. If the scan transmits thedata at offset 1 before t1, B′ may be missed since the change occurredafter offset 1 was scanned and B was transmitted. Similarly, if the scanhas not reached offset 3 before t2, only D′ will be transmitted since Dno longer exists. It may therefore be beneficial to transmit applicationI/Os to data protection appliance 300 if those I/Os write to an offsetthat has already been scanned. If the offset has not been scanned, itmay not be necessary to transmit the application I/Os because the changewill be transmitted when the scan reaches that offset.

Referring back to FIG. 3 and with continued reference to Table 1, offsetmetadata journal entries 310 and offset data journal entries 312 depictthe state of metadata journal 306 and data journal 308 after the initialscan is complete. While there are only four offsets on the scannedstorage system, there are six entries in the journal because the data inoffset 0 and 1 was modified by an application after they were scanned.They each therefore have two entries: B and B′. Segment D was modifiedafter the scan began, but before it was reached. Segment D thereforeonly has one entry: D′.

Metadata journal entries 310 and data journal entries 312 may includeall of the data necessary to synthesize a backup snapshot of the scannedstorage system. Data journal entries 312 may include the actual datafrom the storage system: A, B, B′ C, A′ and D′. Note that data D is notin the data journal 308 since it was modified on the storage systembefore its offset was scanned and transmitted. Metadata journal entries310 may include metadata about the offsets. For example, metadatajournal entries 310 may include an offset identifier, offset length, andwrite time, and volume/device ID. In the present example, metadatajournal entries may include the entries shown in Table 2:

Offset/Time Volume Offset Time 0 A 0 t0 1 A  8 kb t0 2 A  8 kb t1 3 A 16kb t0 4 A 0 t3 5 A 24 kb t2

Table 2's metadata entries may correspond to the states shown inTable 1. The offset at location 0 may be offset 0, the offset at 8 kbmay be offset 1, the offset at 16 kb may be offset 2, and the offset at24 kb may be offset 3. The subscript of each journal entries 310 alsoidentifies the offset associated with that metadata entry.

Deduplicated storage may use metadata journal 306 and data journal 308to synthesize initial backup snapshot 314. First, metadata journal 306may be queried to identify the most recent data associated with eachoffset. Next, the data may be retrieved from journal data file 308 andsynthesized into backup snapshot 314. In some examples, synthesizing thebackup snapshot may include generating and/or copying pointers ratherthan copying entire data blocks. This could be, for example, using aproduct such as EMC® Data Domain® Boost™

For example, once the initial scan is complete, data journal 308includes data A, B, B′, C, A′, and D′. A′ and B′ are the result ofapplication I/Os occurring during the scan process, and thereforerepresent the present state of offsets 0 and 1. To generate backupsnapshot 314, deduplicated storage may therefore retrieve A′, B′, C, andD′ from the data journal 308 and synthesize them together.

Once initial backup snapshot 314 is synthesized, journal entries 310 and312 may no longer be needed. In some examples, they may be removed fromdeduplicated storage 304 in order to conserve space. Alternatively, theymay remain in the journals.

The systems and processes described in reference to FIG. 3 enable asystem to generate an initial backup snapshot. Once the initial snapshotis generated, additional processes may enable continuous data protectionand point-in-time recovery.

Referring to FIG. 4, an example of a process to generate an initialbackup snapshot is a process 400, which includes processing blocks 401,402, 404, 406, 408, 410, 412, 414 and 416. At block 401, sequentialinitialization I/Os are received from a scanned storage volume. TheseI/Os could be, for example, received at a data protection appliance,such as data protection appliance 300. In some examples, theinitialization I/Os are read from the scanned storage volume by the dataprotection appliance.

At block 402, the initialization I/Os are streamed to a deduplicatedstorage. In an example, the deduplicated storage may be substantiallysimilar to deduplicated storage 304. In some examples, theinitialization I/Os are streamed to a data journal using a data stream,and to a metadata journal using a metadata stream. Each stream may be afile in the deduplicated storage. Additionally or alternatively, writesto the journal files may be performed through the EMC® Data Domain®Boost™ API or any other API.

At block 404, the initialization I/Os may be written to a journal on thededuplicated storage. This journal may be, for example, similar tometadata journal 306 and/or data journal 308. In an example, thesejournals may be in the same journal files. Alternatively, these may beseparate files on the deduplicated storage system.

At block 406, application I/Os comprising writes to offsets on thescanned storage volume may be received. These application I/Os may alsobe received at a data protection appliance, such as data protectionappliance 300.

At block 408, an offset associated with a specific application I/O isidentified, and at block 410 it is determined whether the offset hasalready been streamed to the deduplicated storage.

This determination could be made on data protection appliance 300 usingjournal processor 302. If the offset has already been streamed, it musthave already been scanned and included in an initialization I/O. If theoffset has not been streamed, the storage volume scan may not havereached the offset on the storage volume.

At block 412, the application I/O is streamed to the deduplicatedstorage if its offset was included in a previously streamedinitialization I/O. In an example, the application I/O is only streamedwhen its offset was included a previously streamed initialization I/O.Streaming the application I/O when its offset was included in a previousinitialization I/O ensures that writes to the scanned volume are notmissed during the initialization processes. In some examples, theapplication I/Os are streamed to a data journal using a data stream, andto a metadata journal using a metadata stream.

In an example, application Ms are not streamed if they comprise writesto an offset that has not yet been scanned and streamed in aninitialization I/O. This is because the data generated by the write willbe included in the initialization I/O once the scan reaches that offset.This may reduce traffic between the data protection appliance and thededuplicated storage, and may reduce the workload on the deduplicatedbecause the data will only be processed once.

At block 414, the application I/O is written to the journal. Thisjournal may be the same journal as the initialization I/Os, or it may bea separate journal. In an example, the journal is data journal 308and/or metadata journal 306.

At block 416, a backup snapshot is synthesized from the initializationI/Os and the application I/Os. This snapshot may be substantiallysimilar to snapshot 314. In an example, the snapshot is synthesized bygenerating data pointers in a new file on the deduplicated storage.Additionally or alternatively, the pointers may be copied from the datajournal. These pointers may point to the data referenced and/or includedin the journal. Synthesizing the snapshot using pointers may improveperformance, as the data may not need to be replicated.

FIG. 5 depicts an additional or alternative example for initializing abackup snapshot. The system shown in FIG. 5 may include data protectionappliance 500, journal processor 502, and deduplicated storage 504.These elements may be substantially similar to those described inreference to FIG. 3.

Data protection appliance 500 may take a snapshot of a storage systemand transmit that snapshot to deduplicated storage 504 for storage as afile. In an example, this is different than streaming initializationI/Os and synthesizing a snapshot from journal files.

Rather than generating the snapshot on the deduplicated storage, thebackup snapshot is generated using the data protection appliance andtransmitted to deduplicated storage to be stored as backup snapshot 514.

In an example, journal processor 502 may stream application I/Os todeduplicated storage, and those application Ms may be stored in metadatajournal 506 and data journal 508. Like the journals of FIG. 3, metadatajournal 506 may include metadata journal entries 510, and data journal508 may include data journal entries 512. These journals may be used tosynthesize a second backup snapshot or enable point-in-time recovery, asdescribed below.

The systems and processes described in reference to FIGS. 3 to 5 enablea system to generate an initial backup snapshot. Once the initialsnapshot is generated, additional processes may enable continuous dataprotection and point-in-time recovery.

Referring to FIG. 6, a system and process for maintaining backups usingcontinuous data replication is described. As datasets increase in size,backing them up to remote or local backup devices becomes increasinglycostly and complex. Additionally, traditional backup processes may notallow point-in-time recovery since the backups occur on a periodic,rather than continuous, basis. The methods and systems described hereinprovide continuous backup protection as writes are made to a sourcedevice, thereby reducing backup cost and complexity, and may allowingpoint-in-time recovery for backed up files.

The system of FIG. 6 includes a data protection appliance 600, a journalprocessor 602, and a deduplicated storage 604. These elements may besubstantially similar to those described in reference to FIG. 3.Deduplicated storage 604 may include a backup snapshot 614, a metadatajournal file 606, and a data journal file 608. In one example, backupsnapshot file 614 is synthesized in a manner substantially similar tobackup snapshot 314, and may be generated using metadata journal entries610 and data journal entries 612.

As users, applications, and other processes access and use the sourcestorage system, data on that system may change and/or new data may begenerated. As a result, initial backup snapshot 614 may become stale. Ifthe source storage system should fail, there is a chance that any new ormodified data may be lost. To address this concern, data protectionappliance 600 may receive and stream application I/Os to deduplicatedstorage system 604 on a continuous basis, even after initial backupsnapshot 614 is synthesized. Streaming the application I/Os allows thebackups on deduplicated storage 604 to remain up-to-date, withoutneeding to perform additional backups of large datasets. This may reducenetwork traffic, reduce workloads, and conserve space on deduplicatedstorage 604.

For example, new metadata entries 611 and new data journal entries 613represent I/Os made after initial backup snapshot 614 was synthesized.These entries may be written to metadata journal 606 and data journal608, as shown in FIG. 6, or they may be written to separate journalfiles. In FIG. 6, data A′ and C were modified on the source storagedevice, and the journal entries therefore include A″ and C′.

Periodically, new backup snapshots may be synthesized from a previousbackup snapshot and new journal entries. For example, second backupsnapshot 616 may be synthesized from initial backup snapshot 614, newmetadata journal entries 611, and new data journal entries 613. Secondbackup snapshot 616 may be used to restore source storage system up tothe point-in-time the last journal entry was received. That is, backupsnapshot 616 represents a backup of the source storage system at a latertimestamp than initial backup snapshot 614.

In one example, synthesizing second backup journal entry 616 may besubstantially similar to synthesizing the initial backup snapshot 614.Rather than synthesizing all of the data from data journal 608, however,unchanged data may be synthesized from initial backup snapshot 614. Inone example, this synthesis may include copying and/or generating a datapointer. For example, in FIG. 6 the solid arrows between initial backupsnapshot 614 and second backup snapshot 616 represent unchanged datathat is common between the two. In this case, only B′ and D′ remainunchanged. The dashed arrows represent new or changed data that needs tobe synthesized into second backup snapshot 616. In FIG. 6, A′ is changedto A″, C is change to C′. Synthesizing the data into second backupsnapshot 616 therefore results in A″, B′, C′, D′.

Additionally or alternatively, second backup snapshot 616 may besynthesized entirely from journal entries. Rather than synthesizingunchanged data from initial backup 614, deduplicated storage 604 mayretrieve the unchanged data from data journal entries 612. For example,B′ and D′ may be synthesized from data journal entries 612 rather thanfrom initial backup snapshot 614.

Additional backup snapshots, such as second backup snapshot 616, may begenerated periodically or on demand. For example, a user policy mayspecify that new snapshots should be generated every week. Additionallyor alternatively, a user may be preparing to perform some riskyoperations on the source storage system, and may demand that a snapshotbe generated in case something goes wrong. These policies may bemaintained and applied using data protection appliance 600, deduplicatedstorage 604, and/or an external system.

Referring to FIG. 7, an example of a process to maintain backupsnapshots using continuous data replication is a process 700, whichincludes processing blocks 701, 702, 704, 706, 708 and 710. At block701, an initial snapshot of a source storage system may be generated.This initial snapshot may be substantially similar to initial backupsnapshot 614, and may be generated using any one of the processesdescribed in reference to FIGS. 3 to 5. Additionally or alternatively,the initial snapshot may be any previously generated snapshot. Forexample, the initial snapshot may be similar to second backup snapshot616, and may be used in conjunction with journal files to generate athird backup snapshot.

At block 702, application I/Os comprising writes to the source storagesystem may be received. These writes may update existing data orgenerate new data. In some examples, the application I/Os may bereceived by a data protection appliance, such as data protectionappliance 600.

At block 704, the application I/Os may be written to a journal file.This journal file may be substantially similar to metadata journal file606 and/or data journal file 608. In some examples, the application I/Osmay be written to one or more existing journals. Alternatively,application I/Os arriving after a snapshot is synthesized may be writtento their own unique journals. This may be beneficial, for example, whenmaintaining different levels of backup granularity, as described below.

In some examples, the application I/Os are sequentially written to thejournal as they are received. For example, if application I/Os arrive inorder B, C, A, their corresponding entries in the journal will also beB, C, A.

At block 706, a second snapshot may be synthesized from the initialbackup snapshot and the journal. The second snapshot may besubstantially similar to second backup snapshot 616, and the synthesisprocess may be similar to that depicted by the solid and dashed lines.In some examples, the second snapshot may be synthesized entirely fromjournal files rather than use the initial backup snapshot.

During and/or after the synthesis process, additional application I/Osmay be received at block 708. These application I/Os could be used, forexample, to generate the third backup snapshot in the future, and may beprocessed in a manner similar to all the other application I/Osdescribed herein.

At block 710 the additional application I/Os may be written to a journalfile. They may be written to the same journal as the previous I/Os, orthey may be written to a new journal file.

Referring to FIG. 7A, an example of a process to synthesize snapshotsused for continuous data replication is a process 712, which includesprocessing blocks 713, 714, 716 and 718. At block 712, a metadatajournal may be read. This metadata journal could be, for example,metadata journal file 606. In some examples, the metadata journal may beread using a journal processor on a data protection appliance.Additionally or alternatively, the read operation may be local to thededuplicated storage device.

At block 714, the latest I/Os for each offset may be identified. Forexample, metadata journal file 606 includes journal entries 610 and 611.The latest entry for offset 0 is A″, 1 is B′, 2 is C′, and 3 is D′. Insome examples, journal entries 610 and 611 may be written to differentjournals. In such some examples, the only I/Os identified would be A″and C′ since we are synthesizing a snapshot from initial backup snapshot614.

At block 716, a synthesis plan may be generated. This plan may identifywhere each I/O should be synthesized from. For example, the synthesisplan may only identify A″ and C′ for synthesis from data journal 608.The B′ and D′, in contrast, may be obtained from initial backup snapshot614 since they have not changed.

At block 718, the backup snapshot may be synthesized. This backupsnapshot could be, for example, substantially similar to backup snapshot616.

The system and processes described herein may enable additional backupsnapshots to be synthesized from journal entries and existing snapshots.In some examples, the journal entries may be application I/Os which arecontinuously streamed to a data protection appliance. While thesesnapshots may provide additional data protection, they may only allowdata that exists in the snapshots to be recovered. Combining snapshotsand journal files may, however, allow any point-in-time recovery.

When datasets are backed-up on a periodic rather than continuous basis,data recovery may only be available for specific time intervals. Forexample, if a dataset is backed up at the end of every business day, theonly data that is available for recovery is the data as it exists at theend of the day. Continuous backups, however, may allow recovery of dataat any, or nearly any, point-in-time. By transmitting application I/Osto a backup location as they occur, an interim snapshot may besynthesized between scheduled snapshots and data may be recovered.

FIGS. 8 and 9 depict a system and process to synthesize an interimsnapshot for point-in-time recovery. In one example, the system mayinclude data protection appliance 800, journal processor 802, anddeduplicated storage 804. The system may also include metadata journalfile 806, comprising metadata journal entries 810 and 811, and datajournal file 808, comprising data journal entries 812 and 813.

Data protection appliance 800 may receive application I/Os as they aremade to a source storage system. In some examples, journal processor 802may write those I/Os to metadata journal file 806 and data journal file808. Initialization journal entries 810 and 812 may be used tosynthesize initial backup snapshot 814. Metadata entries 811 and datajournal file entries 813 may be application I/Os made to the sourcestorage volume after or while initial backup snapshot 814 wassynthesized. These elements may be substantially similar to thosedescribed in reference to FIG. 6.

In one example, metadata journal entries 811 and data journal entries813 may be used to synthesize interim snapshot 816. Interim snapshot 816may then be used as a source for point-in-time recovery. For example,application I/Os A″ and C′ may be streamed to deduplicated storage asthey are made to the source storage system. A user may then decide theywish recover data from the point-in-time immediately after applicationI/O A″ was streamed. When the user's request arrives, the most recentsnapshot may be initial backup snapshot 814, which does not include A″or C′. To respond to the user's request, deduplicated storage 804 maysynthesize interim snapshot 816. This snapshot may include unchangeddata from initial backup snapshot 814, as shown by the solid blackarrows, and application I/O A″ synthesized from data journal file 808,as shown by the dashed arrow. Note that interim snapshot 816 does notinclude C′. This is because the user requested data recovery at apoint-in-time before C′ may made.

In one example, the data from interim snapshot 816 may be transmittedback to the source storage system and recovered. Additionally oralternatively, it may be exposed to a host as LUN, as described inreference to FIGS. 12 and 13. Interim snapshot 816 may be deleted afterrecovery, or may be retained. In some examples, if interim snapshot 816is generated at a point-in-time sufficiently close to a scheduledsynthesis time, the scheduled synthesis may be cancelled and interimsnapshot 816 may be treated as second backup snapshot 616.

Referring to FIG. 9, an example of a process to perform recovery for apoint-in-time is a process 900, which includes processing blocks 901,902, 904, 906 and 908. At block 901, a request to recover some data isreceived. This request could be, for example, received at dataprotection appliance 800 and/or deduplicated data storage 804. In oneexample, the request may specify a file representing a LUN to recover,or it may be a request to recover an entire system. Additionally oralternatively, the request may specify a point-in-time for the recovery.The point-in-time may be a date, event, or any other mechanism toidentify a specific time. In some examples, the point-in-time may bebetween snapshots.

At block 902, a snapshot nearest the point-in-time may be identified.The snapshot could be, for example, initial backup snapshot 814.

At block 906, a recovery snapshot may be synthesized. This recoverysnapshot could be, for example, substantially similar to interimsnapshot 816. If the recovery snapshot is synthesized using a snapshotfrom an earlier point-in-time, I/Os stored in a journal file may beapplied to synthesize the recovery snapshot.

At block 908 the recovery snapshot may be provided in response to therequest. For example, the recovery snapshot may be exposed as a LUN andmounted on a host computer, or exposed as a network file system share.Additionally or alternatively, the recovery snapshot may be transmittedback to the source storage system. In some examples, only a portion ofthe snapshot, such as a specific file, may be provided.

Combining backup snapshots, journals, and continuous data replicationmay provide point-in-time recovery capabilities. As more data is writtento and/or modified on a source storage system, however, the number ofjournals and snapshots may increase. In some examples, data protectionwindows may be used to manage this data growth.

As the number of snapshots and journals on the deduplicated storagegrows, more space may be required. Deleting snapshots and journals mayresult in important information being lost, and adding to space to thededuplicated storage may be expensive. To address these concerns, backupwindows and policies may be defined. Backup windows may be definedintervals designating which snapshot and journals should be stored, andfor how long.

FIG. 10 depicts a system and process to define backup granularity usingdata protection windows. FIG. 10 shows seventeen snapshot files, labeledS1 through S17, stored on a deduplicated storage device. These snapshotsmay be generated and maintained in a manner substantially similar tothat described above. The deduplicated storage device may also includesix journal files, labeled J1 through J6, which may be used tosynthesize new snapshots or perform point-in-time recovery.

FIG. 10 also includes three data protection windows: short-termprotection window 1000, mid-term protection window 1002, and long termprotection window 1004. Each of these protection windows may have anassociated policy specifying actions to take on any snapshot and/orjournal file within the protection window. For example, one policy maybe “delete all journals within this protection window.” While theexamples described herein address deletion and/or retention policies,any other policy which may be applied to the journals and/or snapshotsis consistent with this disclosure.

Short-term protection window 1000 may be defined to protect bothsnapshots and journal files allowing for point-in-time recovery. Thiswindow may be particularly beneficial for snapshots that were generatedrecently and/or were generated on demand by a user. On demand generationmay signify that the snapshot is more important than a scheduledsnapshot because a user must go out of their way to generate it.Further, it may be more likely that a user needs to recover data whichwas modified or generated recently.

Mid-term protection window 1002 may include only snapshot files. As timeprogresses and journal files move from short-term protection window 1000into mid-term protection window 1002, they may be deleted. Whiledeleting journal files may prevent most point-in-time recovery, thesnapshots may be maintained in mid-term protection window. As a result,some level of point-in-time recovery is preserved. Specifically, anydata included in one of the maintained snapshots may be recovered.Mid-term protection window therefore balances storage needs withrecovery needs.

As snapshots move from mid-term protection 1002 window into long-termprotection window 1004, certain snapshots may be deleted. Point-in-timerecovery may be less important for long-term backups because of theirage. The deleted snapshots may be chosen based on a policy, such as sizeor a user assigned priority. Additionally or alternatively, they may bearbitrarily chosen (for example, only retaining every fifth snapshot).

In some examples, data protection windows may be defined and maintainedusing a data protection appliance, a deduplicated storage device, and/oran external system. For example, if the data protection window isdefined using a deduplicated storage device, that device may delete thejournals and/or snapshots as the move from one data protection windowinto another. In some examples, the data protection windows may changedynamically based on available space on the deduplicated storage device.For example, if there is a large amount of available space theshort-term protection window may be very large, and/or the mid-term andlong-term protection windows may not exist. Similarly, if there is notmuch available space the long-term protection window may be very long.In further examples the short term protection may not exist at all andthe system may use snapshot shipping in order to generate mid- andlong-term snapshots on the deduplicated storage device.

In some examples, a backup system has a limited amount of resources andthe number of files or stream the system can manage is limited. In suchexamples, keeping a file open for each replicated volume is problematic,and thus multiplexing multiple volumes into one file may be required.

Referring to FIG. 11, an example of a data protection system thatincludes volume multiplexing is a data protection system 1100. Thesystem 1100 includes a DPA 1104, a storage array 1106, a backup storagedevice 1116 (e.g., a de-duplication device). The storage array 1106includes a first storage volume 1108 a, a second storage volume 1108 band a third storage volume 1108 c.

The backup storage 1116 includes a consistency group (CG) file 1122,which is a single, concatenated, file that holds data for LUNs (volumes)in a given consistency group. For example, the CG file 1122 includes areplica of the first, second and third storage 1108 a-1108 c. Thevolumes 1108 a-1108 c are replicated to the CG file concurrently. Usingthis approach, resource requirements are reduced to a singlewrite-stream per CG (rather than per replicated LUN (volume)) to thebackup device 1116, which gives an order-of-magnitude reduction in therequirements. That is, volume multiplexing provides a better approachthan copying a file for each volume, which would require a large numberof open files when replicating, as each source LUN maps to a file. Forexample, thousands of LUNs being replicated concurrently would lead tothousands of write-streams to the backup device 1116, which typicallyexceeds the resource requirements of backup devices.

The backup storage 1116 may also include point-in-time (PIT) copies ofthe CG file 1122 (e.g., a first copy of the CG file 1132, a second copyof the CG file 1133 and a third copy of the CG file 1134). In oneexample, a PIT copy is generated periodically.

Each of the PIT copies 1132, 1133, 1134 includes metadata (e.g., thefirst copy of CG file 1132 includes metadata 1144, the second copy of CGfile 1133 includes metadata 1145 and the third copy of CG file 1134includes metadata 1146). In one example, each metadata 1144, 1145, 1146includes a timestamp when the copy of the CG file was generated, a listof volumes that are included in the copy of the CG file and the sizes ofthe volumes.

As further described herein the copies 1132, 1133, 1134 may be used toextract copies of the first, second and third volumes 1108 a-1108 c(e.g., from the first copy of the CG File 1132, a copy of the firststorage volume 1108 a (i.e., volume 1142 a may be extracted) as well asvolumes 1142 b, 1142 c, which are copies of volume 1108 b, 1108 crespectively.

Referring to FIG. 12, a process 1200 is an example of a process toperform snapshot replication to a backup device (e.g., the backupstorage 1116). Process 1200 generates the first snapshot of a set ofvolumes (1202), sends the first snapshot to the backup device by writingthe data to the CG file (1206) and generates a snapshot of the CG file(e.g., first copy of the CG file 1132) (1208). Process 1200 generatesthe next snapshot of the volumes (1210) and sends the differencesbetween the previous and latest snapshot to the CG file (1212). Process1200 generates a snapshot of the CG file (e.g., a second copy of the CGfile 1133) (1214).

Referring to FIG. 13A, an example of the CG file 1122 is the CG file1122′. The CG file 1122 is a multiplexed file that includes concatenatedversions of the volumes 1108 a-1108 c. In this example, the CG file1122′ includes replica of a first storage volume 1108 a′, a replica ofthe second storage volume 1108 b′ and a replica of third storage volume1108 c′. In this example, if the volumes 1108 a-1108 c have sizes of 1GB, 2 GB and 3 GB respectively then the CG file 1122′ will be 6 GB insize and the offset from 0 to 1 GB will be the first replica of thefirst volume 1108′, the offset from 1 GB to 3 GB will be the replica ofthe second volume 1108 b′ and the offset from 3 GB to 6 GB will be thereplica of the third volume 1108 c′.

Referring to FIG. 13B, an example of a first copy of the CG file 1132 isa file 1132′. The file 1132′ is a point-in-time copy of the CG file1122′ and includes metadata 1144′, an example of metadata 1144.

Referring to FIG. 14, a process 1400 is an example of a process toprotect data using the data protection system 1100. Process 1400 copiesa first volume to a consistency group file at the backup device (1402).For example, the DPA 1104 replicates the first storage volume 1108 a tothe CG file 1122.

Process 1400 determines if there are additional volumes to replicate andif there are, process 1400 copies the volumes to the CG file (1406). Forexample, the DPA 1104 replicates the second storage volume 1108 b to theCG file 1122 and the DPA 1104 replicates the third storage volume 1108 cto the CG file 1122.

Referring to FIG. 15, a process 1500 is an example of a process torestore protected data. Process 1500 copies the CG file (1502). Forexample, the CG file 1122 is copied to become the first copy of CG File1132 and the copy process, for example, is a fast copy doing a metadataoperation only.

Process 1500 extracts a volume using synthesis (1506). For example, theprocess in FIG. 9 is used to extract a volume. In one particularexample, to extract a replica of a first volume 1108 a′, the process 900in FIG. 9 is used to copy data from the 0 offset to the 1 GB offset to anew file 1142 a′ of size 1 GB (see FIG. 13C). In one example, the copyoperation for extracting a volume from the CG file is a metadataoperation and does not do any actual data copying and thus is veryefficient.

Process 1500 exposes the extracted volume to the user (1510). Forexample the extracted volume is exposed as a logical unit for a user toaccess.

Referring to FIG. 16, a process 1600 is an example of a process to add avolume to a consistency group (CG) file. Process 1600 receivesnotification that a new volume was added (1602) and adds a volume to theend of the CG file (1606). For example, after a notification is receivedthat a consistency group includes a new volume, the new volume is addedto the end of the CG file 1122, i.e., the file size is increased and thelast offset of the file are part of the new volume. For example, a CGfile 1122″ is formed by placing a new volume 1202 of size 1 GB at theend of the CG file 1122′ (see FIG. 13D).

Referring to FIG. 17, a process 1700 is an example of a process toremove a volume from the CG file. Process 1700 receives notificationthat a volume in a CG file has been removed (1702) and process 1700extracts each volume to a separate file (1706) (e.g., using thesynthesis process (e.g., the process 900 in FIG. 9)). For example, thecopies of the files 1142 a-1142 c are generated (e.g., using the process1400).

Process 1700 copies all the volumes back to a new CG file except thedeleted volume (1708). For example, if the second storage volume isdeleted then copies of the first and third volumes 1142 a, 1142 c arecopied to a CG file 1122′″ (see FIG. 13E).

Referring to FIG. 18, a process 1800 is an example of a process toresize a volume in the CG file in the data protection system of FIG. 11.Process 1800 receives notification that a volume is being resized (1802)and process 1800 extracts each volume to a separate file (1806) (e.g.,using the synthesis process (e.g., the process 900 in FIG. 9)). Forexample, the copies of the files 1142 a-1142 c are generated (e.g.,using the process 1400).

Process 1800 copies all the volumes back to a new CG file accommodatingthe new volume size (1808). For example, if the third storage volume isincreased by 1 GB, then the first, second third volumes from copies 1142a-1142 c are copied to a new CG file 1122″″ (see FIG. 13F).

Referring to FIG. 19, in one example, a computer 1900 includes aprocessor 1902, a volatile memory 1904, a non-volatile memory 1906(e.g., hard disk) and the user interface (UI) 1908 (e.g., a graphicaluser interface, a mouse, a keyboard, a display, touch screen and soforth). The non-volatile memory 1906 stores computer instructions 1912,an operating system 1916 and data 1918. In one example, the computerinstructions 1912 are executed by the processor 1902 out of volatilememory 1904 to perform all or part of the processes described herein(e.g., processes 400, 700, 712, 900, 1200, 1400, 1500, 1600, 1700 and1800).

The processes described herein (e.g., processes 400, 700, 712, 900,1200, 1400, 1500, 1600, 1700 and 1800) are not limited to use with thehardware and software of FIG. 19; they may find applicability in anycomputing or processing environment and with any type of machine or setof machines that is capable of running a computer program. The processesdescribed herein may be implemented in hardware, software, or acombination of the two. The processes described herein may beimplemented in computer programs executed on programmablecomputers/machines that each includes a processor, a non-transitorymachine-readable medium or other article of manufacture that is readableby the processor (including volatile and non-volatile memory and/orstorage elements), at least one input device, and one or more outputdevices. Program code may be applied to data entered using an inputdevice to perform any of the processes described herein and to generateoutput information.

The system may be implemented, at least in part, via a computer programproduct, (e.g., in a non-transitory machine-readable storage medium suchas, for example, a non-transitory computer-readable medium), forexecution by, or to control the operation of, data processing apparatus(e.g., a programmable processor, a computer, or multiple computers).Each such program may be implemented in a high level procedural orobject-oriented programming language to communicate with a computersystem. However, the programs may be implemented in assembly or machinelanguage. The language may be a compiled or an interpreted language andit may be deployed in any form, including as a stand-alone program or asa module, component, subroutine, or other unit suitable for use in acomputing environment. A computer program may be deployed to be executedon one computer or on multiple computers at one site or distributedacross multiple sites and interconnected by a communication network. Acomputer program may be stored on a non-transitory machine-readablemedium that is readable by a general or special purpose programmablecomputer for configuring and operating the computer when thenon-transitory machine-readable medium is read by the computer toperform the processes described herein. For example, the processesdescribed herein may also be implemented as a non-transitorymachine-readable storage medium, configured with a computer program,where upon execution, instructions in the computer program cause thecomputer to operate in accordance with the processes. A non-transitorymachine-readable medium may include but is not limited to a hard drive,compact disc, flash memory, non-volatile memory, volatile memory,magnetic diskette and so forth but does not include a transitory signalper se.

The processes described herein are not limited to the specific examplesdescribed. For example, the processes 400, 700, 712, 900, 1200, 1400,1500, 1600, 1700 and 1800 are not limited to the specific processingorder of FIGS. 4, 7, 7A, 9, 12 and 14 to 18, respectively. Rather, anyof the processing blocks of FIGS. 4, 7, 7A, 9, 12 and 14 to 18 may bere-ordered, combined or removed, performed in parallel or in serial, asnecessary, to achieve the results set forth above.

The processing blocks (for example, in the processes 400, 700, 712, 900,1200, 1400, 1500, 1600, 1700 and 1800) associated with implementing thesystem may be performed by one or more programmable processors executingone or more computer programs to perform the functions of the system.All or part of the system may be implemented as, special purpose logiccircuitry (e.g., an FPGA (field-programmable gate array) and/or an ASIC(application-specific integrated circuit)). All or part of the systemmay be implemented using electronic hardware circuitry that includeelectronic devices such as, for example, at least one of a processor, amemory, a programmable logic device or a logic gate.

Elements of different embodiments described herein may be combined toform other embodiments not specifically set forth above. Variouselements, which are described in the context of a single embodiment, mayalso be provided separately or in any suitable subcombination. Otherembodiments not specifically described herein are also within the scopeof the following claims.

What is claimed is:
 1. A method comprising: replicating a first volumeto a consistency group (CG) file on a backup device; replicating asecond volume to the CG file concurrently with the replicating of thefirst volume, the first and second volumes being in a consistency group;and adding a new volume to the CG file by adding the new volume to theend of the CG file in response to the new volume being added to theconsistency group.
 2. The method of claim 1, wherein the consistencygroup is a first consistency group and the CG file is a first CG file,and further comprising: replicating a third volume to a second CG fileon the backup device; and replicating a fourth volume to the second CGfile, the third and fourth volumes being in a second consistency group.3. The method of claim 1, further comprising generating point-in-timecopies of the CG file.
 4. The method of claim 3, further comprising:receiving a request to restore the first volume at a firstpoint-in-time; extracting the first volume from a point-in-time copycorresponding to the first point-in-time using a synthesis process; andexposing the extracted first volume as a logical unit to a user.
 5. Amethod comprising: replicating a first volume to a consistency group(CG) file on a backup device; and replicating a second volume to the CGfile concurrently with the replicating of the first volume, the firstand second volumes being in a consistency group; and in response to avolume being deleted from the consistency group: extracting each volumein the CG file to a separate file; and copying volumes to a new CG fileexcept the volume being deleted.
 6. The method of claim 5, furthercomprising generating point-in-time copies of the CG file.
 7. The methodof claim 6, further comprising: receiving a request to restore the firstvolume at a first point-in-time; extracting the first volume from apoint-in-time copy corresponding to the first point-in-time using asynthesis process; and exposing the extracted first volume as a logicalunit to a user.
 8. A method comprising: replicating a first volume to aconsistency group (CG) file on a backup device; and replicating a secondvolume to the CG file concurrently with the replicating of the firstvolume, the first and second volumes being in a consistency group; andin response to resizing a volume in the consistency group: extractingeach volume in the CG file to a separate file; and copying volumes tonew CG file accommodating the resized volume.
 9. The method of claim 8,further comprising generating point-in-time copies of the CG file. 10.An apparatus, comprising: electronic hardware circuitry configured to:replicate a first volume to a consistency group (CG) file on a backupdevice; replicate a second volume to the CG file concurrently with thereplicating of the first volume, the first and second volumes being in aconsistency group; in response to a volume being deleted from theconsistency group: extract each volume in the CG file to a separatefile; and copy volumes to a new CG file except the volume being deleted.11. The apparatus of claim 10, wherein the circuitry comprises at leastone of a processor, a memory, a programmable logic device or a logicgate.
 12. The apparatus of claim 10, further comprising circuitryconfigured to add a new volume to the CG file by adding the new volumeto the end of the CG file in response to the new volume being added tothe consistency group.
 13. The apparatus of claim 10, further comprisingcircuitry configured to, in response to resizing a volume in theconsistency group: extract each volume in the CG file to a separatefile; and copy volumes to new CG file accommodating the resized volume.14. The apparatus of claim 10, further comprising circuitry configuredto generate point-in-time copies of the CG file.
 15. The apparatus ofclaim 14, further comprising circuitry configured to: receive a requestto restore the first volume at a first point-in-time; extract the firstvolume from a point-in-time copy corresponding to the firstpoint-in-time using a synthesis process; and expose the extracted firstvolume as a logical unit to a user.
 16. An article comprising: anon-transitory computer-readable medium that stores computer-executableinstructions, the instructions causing a machine to: replicate a firstvolume to a consistency group (CG) file on a backup device; andreplicate a second volume to the CG file concurrently with thereplicating of the first volume, the first and second volumes being in aconsistency group; in response to resizing a volume in the consistencygroup: extract each volume in the CG file to a separate file; and copyvolumes to new CG file accommodating the resized volume.
 17. The articleof claim 16, further comprising instructions causing the machine to adda new volume to the CG file by adding the new volume to the end of theCG file in response to the new volume being added to the consistencygroup.
 18. The article of claim 16, further comprising instructionscausing the machine to, in response to a volume being deleted from theconsistency group: extract each volume in the CG file to a separatefile; and copy volumes to a new CG file except the volume being deleted.19. The article of claim 16, further comprising instructions causing themachine to generate point-in-time copies of the CG file.
 20. The articleof claim 19, further comprising instructions causing the machine to:receive a request to restore the first volume at a first point-in-time;extract the first volume from a point-in-time copy corresponding to thefirst point-in-time using a synthesis process; and expose the extractedfirst volume as a logical unit to a user.